Chesapeake Bay Program Indicator Framework
Reporting Level Indicators
Indicator and Data Survey
A. Category/Name/Source/Contact
(1) Category of Indicator
_x_ Factors Impacting Bay and Watershed Health
___ Restoration and Protection Efforts
___ Watershed Health
___ Bay Health
(2) Name of Indicator: Bay Watershed Population
(3) Data Set Description:



For what purpose(s) were the data collected? (e.g., tracking, research, or longterm monitoring.) - Long-term monitoring.
Which parameters were measured directly? N/A.
Which were obtained by calculation?
o The 1950 – 2000 and 2010 data are based on decadal US Census Bureau
data apportioned to the Bay watershed by the CBPO.
o The 2001 – 2009, and 2011 - 2014 data are based on the annual population
estimates produced by the US Census Bureau apportioned to the Bay
watershed by the CBPO.
o The 2020, 2030, 2040 data are based on County population projections
produced by each state and the Washington Council of Governments and
apportioned to the Bay watershed by the CBPO.
(4) Source(s) of Data: Peter Claggett, 410-267-5771, PClagget@chesapeakebay.net
 Is the complete data set accessible, including metadata, data-dictionaries and
embedded definitions? If yes, please indicate where complete dataset can be
obtained. (5) Custodian of Source Data (and Indicator, if different): Peter
Claggett, 410-267-5771, PClagget@chesapeakebay.net
(6) CBPO Contact: Peter Claggett, 410-267-5771, PClagget@chesapeakebay.net
B. Communication Questions (complete either part 1, 2, or 3)
3. Factors Impacting Bay and Watershed Health indicators only
(7c) What is the long-term trend? (since start of data collection)
From 1950 through 2014, the Bay watershed’s population increased from 8,382,880 to
17,986,329
(8c) What is the short-term trend? (10-year trend)
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Between 2000 and 2010, the watershed’s population increased 10.6 percent. This is
compared to a 10.3 percent increase in the 1990s and an 11.6 percent increase in the
1980s.
(9c) What is the current status?
As of 2014, 17,986,329 people were estimated to live in the Bay watershed, up from
17,875,019 in 2013. Note that all inter-decennial census population estimates are revised
annually until the next decennial census (e.g., year 2020). For example, the 2011-2013
were revised with the release of the 2014 estimates.
(10c) What does this indicator tell us?
•
While the overall population of the Bay watershed continues to grow, population
changes vary from state to state and region to region. Some areas are gaining
population due to a combination of births, declining deaths, and migration, while
populations in other areas are leveling out or declining.
•
Experts predict that the watershed’s population will increase to over 21 million by
the year 2040.
(11c) Why is it important to report this information?
•
The way humans use the land has the greatest impact on the Bay and local
waterways. Natural areas like forests and wetlands have a positive effect on water
quality, while areas developed for farming or cities generally have a negative
impact.
•
The decline in the health of the Chesapeake Bay is correlated to the rise in
population in the watershed: since 1950, the number of residents has more than
doubled. Projections through 2040 show continued population growth, loss of
natural areas and increases in urban development, which are all challenges to
protecting and restoring the Chesapeake. While the rate of growth is expected to
decline over the coming decades, absolute growth is expected to continue to
exceed 1 million per decade.
•
Even more influential than population growth impacts to the Bay are the
corresponding impacts from development. Trends from the 1950’s to mid-2000’s
show people moving into sprawling suburbs and living in bigger houses on larger
lots, causing forests, farms and other valuable lands to be transformed into
subdivisions, shopping centers and parking lots. This land conversion severely
impacts the health of streams, rivers and the Bay. More recent trends suggest a
possible resurgence of growth in urbanized areas with an increasing proportion of
new housing stock represented by multi-unit dwellings (as opposed to singledetached homes). This is a promising phenomenon because urbanized areas have
infrastructure such as roads, schools, and sewer systems to support future growth
while minimizing increases in impervious surfaces and wastewater discharges.
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•
Impervious surfaces such as roads, rooftops, and parking lots do not allow water
to filter into the ground. Instead rainfall runs off, picking up pollution and quickly
carrying it into waterways.
(12c) What detail and/or diagnostic indicators are related to this reporting level
indicator?
N/A
4. All indicators
(7d) What did the most recent data show compared to the previous year? As of 2014,
17.99 million people were estimated to live in the Bay watershed, up from 17.88 million
in 2013.
(8d) If this was a significant increase/decrease:

To what do you attribute it? N/A

Is this educated speculation or actual cause? N/A
(9d) What is the goal, target, threshold or expected outcome for this indicator? N/A
(10d) Was a new goal, target, threshold or expected outcome established since last
reporting? N/A Why? N/A
(11d) Did the methodology of data collection or analysis change from previous year(s)?
no Why and how? N/A

If so, how will this improve your/our future work? N/A
C. Temporal Considerations
(13) Data Collection Date(s):
Population:
 The 1950 – 2000 and 2010 data are based on decadal US Census Bureau data
apportioned to the Bay watershed by the CBPO.
 The 2001 – 2009, and 2011 - 2014 data are based on the annual population
estimates produced by the US Census Bureau apportioned to the Bay watershed
by the CBPO.
 The 2020, 2030, and 2040 data are based on County population projections
produced by each state and the Washington Council of Governments and
apportioned to the Bay watershed by the CBPO.
(14) Planned Update Frequency ~ annually in July to August timeframe:
(a) Source Data: Population: every year
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b) Indicator: Population: every year
(15) For annual reporting, month spatial data is available for reporting: N/A
D. Spatial Considerations
(16) Type of Geography of Source Data (point, line polygon, other): The population data
is a county spreadsheet that can be linked to county TIGER polygon files via common
FIPS field.
(17) Acceptable Level of Spatial Aggregation (e.g. - county, state, major basin, tributary
basin, HUC):
Entire watershed
(18) Are there geographic areas with missing data? If so, where?
N/A
(19) The spatial extent of this indicator best described as:
(a) Chesapeake Bay (estuary)
(b) Chesapeake Bay Watershed
(c) Other (please describe): _______________________
Please submit any appropriate examples of how this information has been mapped or
otherwise portrayed geographically in the past.
(20) Can appropriate diagnostic indicators be represented geographically?
N/A
E. Data Analysis and Interpretation: (Please provide appropriate references and
location of documentation if hard to find.)
(21) Is the conceptual model used to transform these measurements into an indicator
widely accepted as a scientifically sound representation of the phenomenon it indicates?
(i.e., how well do the data represent the phenomenon?)
There are many acceptable ways to apportion county population to watershed boundaries.
We used a population and residential road weighted allocation method outlined in
Claggett, P. and C. Bisland, 2004, Assessing the vulnerability of forest and farmlands to
development in the Chesapeake Bay watershed, in Proceedings of the IASTED
International Conference on Environmental Modeling and Simulation, November 22-24,
2004, St. Thomas, U.S. Virgin Islands.
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(22) What is the process by which the raw data is summarized for development and
presentation of the indicator?
For the population data, see Claggett, P. and C. Bisland, 2004, Assessing the
vulnerability of forest and farmlands to development in the Chesapeake Bay watershed,
in Proceedings of the IASTED International Conference on Environmental Modeling and
Simulation, November 22-24, 2004, St. Thomas, U.S. Virgin Islands.
(23) Are any tools required to generate the indicator data (e.g. - Interpolator, watershed
model)
Geographic Information System software and spreadsheet software.
(24) Are the computations widely accepted as a scientifically sound?
The population methods have been published in the proceedings of a scientific
conference and the impervious surface mapping methods have been published in a peerreviewed scientific journal.
(25) Have appropriate statistical methods been used to generalize or portray data beyond
the time or spatial locations where measurements were made (e.g., statistical survey
inference, no generalization is possible)?
N/A
(26) Are there established reference points, thresholds or ranges of values for this
indicator that unambiguously reflect the desired state of the environment?
(health/stressors only)
N/A
F. Data Quality: (Please provide appropriate references and location of documentation
if hard to find.)
(27) Were the data collected according to an EPA-approved Quality Assurance Plan?
If no, complete questions 28a – 28d:
No
(28a) Are the sampling design, monitoring plan and/or tracking system used to collect the
data over time and space based on sound scientific principles?
Yes.
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(28b) What documentation clearly and completely describes the underlying sampling and
analytical procedures used?
Claggett, P. and C. Bisland, 2004, Assessing the vulnerability of forest and farmlands to
development in the Chesapeake Bay watershed, in Proceedings of the IASTED
International Conference on Environmental Modeling and Simulation, November 22-24,
2004, St. Thomas, U.S. Virgin Islands.
(28c) Are the sampling and analytical procedures widely accepted as scientifically and
technically valid?
Yes.
(28d) To what extent are the procedures for quality assurance and quality control of the
data documented and accessible?
See above references.
(29) Are the descriptions of the study or survey design clear, complete and sufficient to
enable the study or survey to be reproduced?
Yes.
(30) Were the sampling and analysis methods performed consistently throughout the data
record?
Yes.
(31) If datasets from two or more agencies are merged, are their sampling designs and
methods comparable?
Only the population projections were derived by different agencies using potentially
different methods and slightly different assumptions. It is not yet known the degree to
which the methods used by each state are comparable.
(32) Are uncertainty measurements or estimates available for the indicator and/or the
underlying data set?
No.
(33) (Do the uncertainty and variability impact the conclusions that can be inferred from
the data and the utility of the indicator?
Yes.
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(34) Are there noteworthy limitations or gaps in the data record? Please explain.
G. Additional Information (optional)
(35) Please provide any other information about this indicator you believe is necessary to
aid communication and any prevent potential miss-representation.
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